A 35-year-old multipara died suddenly of a pulmonary embolism about 12 h after delivery. The morphological features and the entry site of the emboli into the circulation suggested that they were decidual cells. Intact decidual cells accounted for only a minority of the emboli: the great majority were cells that had lost their nuclei and/or had been fragmented. The presence of embolized areas, accompanied by fibroblasts and newly formed capillaries, suggested that the embolization process had started before the beginning of labor. However, no symptoms suggesting embolism had been recorded on the clinical chart.